# Analysis of the Microbiota of Milk from Holstein–Friesian Dairy Cows Fed a Microbial Supplement

## TL;DR

This study shows that feeding dairy cows a lactobacilli supplement changes their milk microbiota and improves milk production over 16 months.

## Contribution

The study identifies specific microbial taxa associated with milk production traits and demonstrates the long-term impact of DFM supplementation on milk microbiota.

## Key findings

- DFM supplementation significantly altered the milk microbiota composition in dairy cows.
- Twenty-six genera, including Pseudomonas and Lactococcus, were associated with differences between supplemented and non-supplemented cows.
- Microbial taxa like Turicibacter and Bifidobacterium were linked to milk production and quality traits.

## Abstract

This study reports the investigation of the effects of a lactobacilli-based direct-fed microbial (DFM) supplement on milk microbiota and production of dairy cows over a 16-month period. Significant differences between cows receiving the supplement compared to those that did not were identified. Supplementation with a DFM can improve dairy cow productivity, including increasing the quality and quantity of milk produced. An understanding of how these supplements influence the existing microbiota is critical in optimizing their use, formulation, and effectiveness and for enhancing animal health and welfare. This research highlights the potential of using DFMs to improve the efficiency of the dairy industry.

Previous studies of direct-fed microbial (DFM) supplements showed variable effects on the microbiota and physiology of dairy cows. The main aims of this study were to investigate the milk microbiota of cows supplemented with a lactobacilli-based DFM compared to untreated cows; describe the changes; and quantify the association between the taxa and cow productivity. The study followed seventy-five Holstein–Friesian dairy cows supplemented with a DFM over 16 months compared to seventy-five non-supplemented cows. Twenty-five cows from each group were sampled for microbiota analysis. The top taxa significantly associated with the variables were as follows: Age (Mammaliicoccus_319276, Turicibacter), milk production (Turicibacter, Bifidobacterium_388775), DIM (Stenotrophomonas_A_615274, Pedobacter_887417), milk fat percentage (Pseudomonas_E_647464, Lactobacillus), calendar month (Jeotgalicoccus_A_310962, Planococcus), milk protein percentage (Tistrella, Pseudomonas_E_650325), experimental group (Enterococcus_B, Aeromonas), SCC (Paenochrobactrum, Pseudochrobactrum), and trimester of pregnancy (Dyadobacter_906144, VFJN01 (Acidimicrobiales)). These were identified using multivariable analysis. Twenty-six genera were associated with the differences between experimental groups, including Pseudomonas, Lactococcus and Staphylococcus. Microbial taxa that changed in relative abundance over time included Atopostipes, Brevibacterium and Succinivibrio. Many of these genera were also part of the core microbiota. Supplementation with the DFM significantly altered the milk microbiota composition in the dairy cows, highlighting the impact of long-term DFM supplementation on microbial communities.